1. Field of the Invention
The present invention relates to an optical disc drive for reading and/or writing information from/on a disk storage medium (e.g., an optical disc) stored in a cartridge.
2. Description of the Related Art
Various types of disk storage media such as CDs and DVDs, from/on which information can be read and/or written using a light beam, have become very popular these days. Those disk storage media will be simply referred to herein as “discs”. Accordingly, optical disc drives are now used extensively to read and/or write information from/on these discs. Also, in order to store video information on those discs, techniques of increasing the storage densities of discs have been quickly developed day after day.
In order to increase the storage density of a disc, recording marks or pits on the disc or the spot size of a light beam for use in read and write operations need to be reduced. For that purpose, in an optical disc drive, the laser diode, functioning as the light source of the light beam, has a shortened wavelength and the lens to focus the light beam has an increased numerical aperture (NA).
However, as the recording marks, pits and spot size of the read/write light beam are reduced, the dust, finger marks and scratches to be attached to, or done on, the surface of a disc are more and more likely to affect the information being read or written. Thus, a cartridge to protect the disc surface from those harmful matters has become increasingly important lately.
A conventional optical disc drive, which is designed to process an optical disc in a cartridge, may include a spindle motor for rotating and driving the disc, an optical head for reading and/or writing information from/on the disc, and a traverse base holding the spindle motor and optical head thereon, for example. The traverse base includes a positioning member for positioning the cartridge. After the cartridge has been loaded into the disc drive by a loading mechanism, the traverse base is elevated and driven, thereby clamping the disc in the cartridge onto the spindle motor. In such a configuration, however, the positioning member for positioning the cartridge needs to be mounted on the traverse base, thus making the traverse base bigger and also making it difficult to reduce the overall size and weight of the drive or the manufacturing cost thereof. In addition, heavier load is placed on the motor for elevating and driving the traverse base, and therefore, a lot of noise is produced.
Japanese Laid-Open Publication No. 2003-217214 discloses another conventional optical disc drive to process a disc in a cartridge. In this optical disc drive, the traverse base is separated from the positioning member to overcome the problem described above. As shown in FIG. 11, that type of optical disc drive includes a body 100 and is designed so as to accommodate a cartridge 102 in which a disc 101 is stored. Hereinafter, it will be described how this optical disc drive operates after having been loaded with the cartridge 102 and until getting ready to perform a read or write operation on the optical disc 101.
First, the operator puts the cartridge 102, including the disc 101, on a tray 103. The tray 103 is supported on a bottom chassis 106 so as to be movable in a loading/unloading direction A. A loading motor 108 is provided on the bottom chassis 106 and its rotation is transmitted to a rack on the back surface of the tray 103 by way of a loading gear system 109, thereby pulling the tray 103 into the body 100.
The shutter 102a of the cartridge 102 is opened and closed by an opener 105 provided for the tray 103. The opener 105 is provided so as to slide in the direction in which the shutter 102a moves while the cartridge 102 is mounted on the tray 103 and the tab of the opener 105 contacts with a protrusion of the shutter 102a. A pin is provided for the opener 105 so as to interlock with a cam groove of an upper chassis 107. As the tray 103 is pulled in, the pin goes along the cam groove, thereby sliding the opener 105 and the shutter 102a as well.
As soon as the tray 103 has been pulled in, the operation of moving a clamper to clamp the optical disc 101 starts. A clamp arm 125 is supported so as to rotate at the middle with respect to the upper chassis 107. A clamper 124 is provided at one end of the clamper arm 125, while a bent portion is provided at the other end of the clamper arm 125. The clamper 124 is made up of two vertically splitting members and is designed such that the upper and lower members of the clamper 124 sandwich the edge of an opening of the clamper arm 125 with some gap provided between them. Accordingly, the clamper 124 is supported so as to rotate with respect to the clamper arm 125. While the tray 103 is drawn out of the body 100, the bent portion protrudes toward the back surface of the upper chassis 107 and the clamper 124 protrudes upward from the upper surface of the upper chassis 107.
When the tray 103 has been pulled in the body 100, a portion of the tray 103 pushes up the bent portion of the clamper arm 125. As a result, the clamper arm 125 rotates, thereby pressing the clamper 124 down. As a result of the opening operation of the shutter 102a as described above, the clamp area of the disc 101 is exposed and the clamper 124 that has been pressed down is now located right over the clamp area of the disc 101. In this manner, the clamping operation gets ready.
Next, a cartridge positioning operation will be described with reference to FIGS. 11, 12 and 13. FIGS. 12 and 13 illustrate the structures of a positioning pin piece 118 and a slide cam 123 for use to position the cartridge 102.
The positioning pin piece 118 includes a positioning pin 118a to close a positioning hole 102b of the cartridge 102 and a pair of convex portions 118b. These convex portions 118b fit with the cam grooves 123a of the slide cam 123 so as to slide along the grooves 123a. Accordingly, as the slide cam 123 shifts in the direction D, the positioning pin 118a moves upward in the direction C.
The slide cam 123 is secured to the bottom chassis 106 so as to slide perpendicularly to the loading/unloading direction A of the tray 103. The sliding protrusion 123b of the slide cam 123 fits with, and slides along, a grooved load cam (not shown) on the back surface of the tray 103. The slide cam 123 further includes a rack portion 123c that engages with the loading gear system 109.
The load cam provided on the back surface of the tray 103 includes a sloped portion to move the slide cam 123 slightly in the vicinity of an insert position where the tray 103 is pulled in completely and an extended portion for keeping on guiding the sliding protrusion 123b perpendicularly to the direction in which the tray 103 is shifting. Accordingly, just before the tray 103 has been pulled in fully as a result of the rotation of the loading motor 108, the sloped portion of the load cam drives the slide cam 123 a little, thereby starting to engage the rack portion 123c of the slide cam 123 with the loading gear system 109. Even after the rack portion 123c of the slide cam 123 has disengaged itself from the loading gear system 109 to complete the insertion, the slide cam 123 keeps on sliding along the extended portion of the load cam. The slide cam 123 drives the positioning pin piece 118 along the cam grooves 123a, thereby inserting the positioning pin 118a into the positioning hole 103a of the cartridge. In this manner, the cartridge 102 can be fixed at a predetermined position.
An assist arm 135 for assisting the elevation of the positioning pin piece 118 is provided in a rotatable state for the bottom chassis 106 and is driven as the slide cam 123 slides. If the cartridge 102 has shifted significantly within the tray 103, then an insertion force to correct the shift of the cartridge 102 is needed in inserting the positioning pin piece 118 into the positioning hole 102b. Accordingly, the assist arm 135 assists the elevation of a portion surrounding the positioning pin 118a, thereby preventing the positioning pin piece 118 from being distorted or deformed. Also, the assist arm 135 contributes to inserting the positioning pin 118a into the positioning hole 102b in one way or another, thereby correcting the shift of the cartridge 102.
Also, an adjust plate 136 is further provided for the bottom chassis 106 to regulate the instability of the positioning pin piece 118 in the loading/unloading direction A. Thus, the positioning pin 118a can have its position in the loading/unloading direction A regulated and is fixed to the bottom chassis 106.
The traverse base 112 supports a spindle motor 113 to mount and rotate the disc 101 thereon and an optical head 114, which can be shifted by a guide shaft 115 in the radial direction of the disc 101 so as to perform read and write operations on the disc 101. The traverse base 112 is elastically held by a traverse holder 117 with rubber dampers 120 provided at the four corners. Two rotation sub-shafts 117a are provided on two side surfaces of the traverse holder 117 and are arranged on a plane that is defined parallel to the surface of the disc 101. By engaging the rotation sub-shafts 117a with the bearings 106a of the bottom chassis 106, the traverse base 112 can be supported so as to rotate on the rotation sub-shafts 117a. 
Cam followers 117b stick out of a side surface of the traverse holder 117 so as to face the slide cam 123 and fit with, and slide along, the cam grooves 123a. As the slide cam 123 slides, the traverse holder 117 and traverse base 112 rotate on the sub-shafts 117a and elevate upward. As a result, the spindle motor 113 is also elevated and the disc 101 is mounted on the turntable 113a. Also, due to an attraction between a magnetic body embedded at the top center of the spindle motor 113 and a magnet included in the clamper 124, the clamper 124 presses the disc 101 toward the turntable 113a. In this manner, the clamping operation is finished.
The positioning pin piece 118 also fits with and slides along the cam grooves 123a of the slide cam 123. Accordingly, as the slide cam 123 slides, first, the positioning pin piece 118 elevates to perform the cartridge positioning operation described above, and then the traverse holder 117 elevates after a while, thereby mounting the disc 101 on the spindle motor 113.
In an optical disc drive having such a structure, the traverse base is provided separately from the positioning member. Thus, the size of the traverse base can be reduced, the load on the motor to elevate and drive the traverse base can be lightened, and the noise produced can be minimized.
However, in the optical disc drive disclosed in Japanese Laid-Open Publication No. 2003-217214, the positioning pin for positioning the cartridge should be a member that is independent of the traverse base. In addition, the assist lever to assist the movement of the positioning pin and the adjust plate for positioning control are also needed, thus increasing the number of members that make up the optical disc drive and increasing the manufacturing cost, too.
Generally speaking, the smaller the number of components intervening between the disc and the cartridge, the smaller the sum of errors between the disc and the cartridge and the higher the positional accuracy should be. Nevertheless, in the optical disc drive disclosed in Japanese Laid-Open Publication No. 2003-217214, there are as many as six components (namely, the spindle motor, traverse base, rubber dampers, traverse holder, bottom chassis and positioning pin) between the disc and the cartridge. For that reason, the position of the positioning pin must be precisely controlled with respect to the disc motor, thus increasing the number of manufacturing process steps and the manufacturing cost. Also, the traverse holder holds the overall traverse base to increase the size and cost of that member and make it difficult to downsize the overall drive.